In present day apparatus, for the measurement of the mass of fuel within a fuel tank such as a fuel tank used on aircraft, a capacitive type unit is commonly employed. Such a capacitive type measuring unit is generally in the form of a probe inserted into the fuel tank so that its capacitance varies as a function of the liquid level as well as the dialectric constant of the fuel. Generally, a series capacitor of a fixed value is also utilized in such a capacitive probe unit for compensation so that the output of the probe varies directly as the mass of the sensed fuel. Heretofore, such a compensating capacitor has been mounted on the probe, adding to the complexity of the unit. In addition, this series capacitor has a critical value and must be selected for one specific fuel, so that the aircraft must use the specific fuel for which the series capacitor is designed or change probe units for each type of fuel used. Furthermore, since the series capacitor is mounted on the probe, it is exposed to the rather harsh tank environment so that its useful life is shortened and a premature failure of the probe is not uncommon.